The present invention relates to torches and more particularly to self-igniting torches.
Torches which utilize combustible gases, such as propane or Mapp.RTM. gas from a cylinder under pressure, are widely known in the art. Such torches are used for soldering, heating and burning, among other uses. The fuel is generally maintained in a cylinder or other container under pressure, and is released from the cylinder through an adjustable valve passing through a conduit to a burner head. The jet of gas passing out of an orifice is mixed with air to form a combustible mixture ignited in the form of a flame which is used for various purposes. The cylinder is usually remote from the torch head and is generally in the form of a portable hand-held cylinder with the torch head and valve mounted directly thereon. This type of portable torch and cylinder constitute generally the disposable liquid propane gas cylinder type that is widely used. Torches such as those described above are disclosed in U.S. Pat. Nos. 3,612,037; 3,994,674 and 4,332,550.
Known torch head assemblies conventionally have a valve body including an adjustable needle stem and a tube leading from the valve housing with a gas orifice or spud disposed in the tube considerably spaced from the valve housing and followed by air holes wherein the gas is mixed with air and thereafter proceeds to a flameholder at the other end of the tube. A flameholder is shown in U.S. Pat. No. 4,013,395 as item 116.
One disadvantage of many torches is the need for ignition by an external spark generator such as a hand-held friction device and this problem has been addressed to some extent in U.S. Pat. No. 4,013,395 which concerns an aerodynamic fuel combuster, showing a spark generator 17 which activates a spark plug 15 when pushbutton 19 is depressed and U.S. Pat. No. 3,843,311 which describes a piezoelectric device for igniting a lantern wherein piezoelectric element is activated when resilient member 68 is depressed.
However, in self-ignitable torches problems could arise in conjunction with the location of ignition devices, e.g., ignition wires, retaining clips, venturis etc., upstream of the flameholder. Such ignition wires and retainer clips could result in burning not only downstream of the flameholder, but also between the orifice and the flameholder. This could result in severe overheating of the burner tube and a reduction in combustion intensity.